为探究滨海盐沼湿地植被生长季生态系统CO2交换特征和影响机制,以辽河口芦苇盐沼湿地为研究对象,采用涡度协方差技术观测净生态系统CO2交换(NEE)特征,并分析了光合有效辐射(PAR)、气温(Ta)等环境因子和生物量对CO2交换的影响.结果表明:生长季内植被总初级生产力(GPP)、生态系统呼吸(Reco)和NEE各月日平均变化曲线分别呈倒"U"型、横向"S"型和"U"型.CO2交换也表现出明显的季节变化规律,GPP和|NEE|在6月累计值最大(分别为273.5、210.5 gC·m-2),Reco在7月累计值最大(76.7 g C·m-2).白天PAR是NEE的主控因子,NEE与PAR符合直角双曲线关系,PAR可解释NEE变异的37.7％～51.6％,且光曲线拟合参数在6月达到最大值.夜晚呼吸(Reco,night)受Ta、10cm深土壤含水量(SWC10)的协同影响.在不同SWC10范围下,Reco,night与Ta均呈指数相关关系.当SWC10≤35％时,Reco,night值集中于生长季初期和末期,温度敏感性(Q10)为1.44;当SWC10＞35％时,Reco,night值集中于生长季中期(Q10为1.97)和旺盛期(Q10为2.03).2020年生长季,辽河口芦苇盐沼湿地表现为CO2汇,NEE为-693 g C·m-2,GPP为1043 g C·m-2,Reco为 350 g C·m-2.
CO2 exchange and its influencing mechanisms in a reed salt marsh in the Liaohe River estuary during the growing season
To investigate the characteristics and influencing mechanisms of ecosystem CO2 exchange in salt marsh,we monitored net ecosystem CO2 exchange(NEE)using the eddy covariance technique,and analyzed the effects of photosynthetically active radiation(PAR),temperature(Ta)and biomass on CO2 exchange in Liaohe River estuary during the growing season.The results showed that the daily average curves of gross primary productivity(GPP),ecosystem respiration(Reco)and NEE of each month showed inverted'U',horizontal'S'and'U'shape,re-spectively.There was seasonal variation for CO2 exchange.GPP and|NEE|reached the maximum cumulative values in June(273.5 and 210.5 g C·m-2,respectively)and Reco reached the maximum cumulative value in July(76.7 gC·m-2).PAR was the dominant factor of NEE in daytime,with a rectangular hyperbola relationship.PAR explained 37.7％to 51.6％variation of NEE.The parameter of light fitting curve reached a maximum in June.Ta and soil water content at 10 cm depth(SWC10)synergistically influenced nighttime respiration(Reco,night).Reco,night and Ta showed exponential correlations at different SWC10 levels.When SWC10≤35％,Reco night values were derived from early and late growing season,and the temperature sensitivity(Q10)was 1.44.When SWC10＞35％,Reco,night values were derived from middle(Q10=1.97)and vigorous period(Q10=2.03)of the growing season.In the grow-ing season of 2020,the reed salt marsh at the Liaohe River estuary acted as a CO2 sink,with the NEE,GPP,and Reco being-693,1043,and 350 g C·m-2,respectively.
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